BAHADIR AKBAL
Electrical
- Jul 4, 2025
- 1
Hello everyone
There is a YNd11 step-up transformer in a factory. When the star point of the transformer is grounded, the protection relay gives a phase ground fault approximately 20 minutes later. The same problem occurs when the delta winding of the transformer is completely unloaded. The star side is at 33 kV, the delta side is at 6.3 kV. If the star point is not grounded, it does not give a fault. The fault current is reported by the protection relay as approximately 30 A. It is a great risk for the star side to work without grounding. However, when grounding is done, the protection relay trips. Do you have any information on this subject? Can the 3rd harmonics in the network or in the transformer's idle operation reach the level of 30 A?
There is a YNd11 step-up transformer in a factory. When the star point of the transformer is grounded, the protection relay gives a phase ground fault approximately 20 minutes later. The same problem occurs when the delta winding of the transformer is completely unloaded. The star side is at 33 kV, the delta side is at 6.3 kV. If the star point is not grounded, it does not give a fault. The fault current is reported by the protection relay as approximately 30 A. It is a great risk for the star side to work without grounding. However, when grounding is done, the protection relay trips. Do you have any information on this subject? Can the 3rd harmonics in the network or in the transformer's idle operation reach the level of 30 A?
